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Endocrinology > Reproduction/ Sex steriod axis > Flashcards

Reproduction/ Sex steriod axis Flashcards

1
Q

what 2 gonadotrophic hormones are secreted by the pituitary gland

A

FSH and LH

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2
Q

what does FSH do in males

A

causes the testes to produce sperm

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3
Q

what does FSH do in females

A

causes the growth of ovarian follicles (oogenesis) and causes the ovary to secrete oestrogen

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4
Q

what does LH do in males

A

causes the testes to secrete testosterone

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5
Q

what does LH do in females

A

causes ovulation and progesterone production by the corpus luteum

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6
Q

how does testosterone affect levels of LH, FSH and GnRH

A

when high will reduce the levels of LH and FSH and GnRH by negative feedback HPG axis

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7
Q

what is the HPG axis

A

hypothalamus - anterior pituitary - LH and FSH - ovaries (oestrogen and progesterone) and testes (testosterone)

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8
Q

what hormone causes the release of FSH and LH from the anterior pituitary

A

gonadotrophin releasing hormone GnRH)

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9
Q

what type of hormone if GnRH and what makes and releases it

A

neuropeptide hormone

made and released by GnRH neurones within the hypothalamus

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10
Q

how is GnRH released in both males and females

A

in a pulsatile manner

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11
Q

what is the different between GnRH secretion in males and females

A

males- constant pulses

females- frequency of pulses varies depending on menstrual cycle (1-2 hours during early follicular phase, decreasing to 4 hours during luteal phase)

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12
Q

what do high frequency GnRH pulses stimulate

A

LH pulses

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13
Q

what do low frequency GnRH pulses allow

A

FSH release

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14
Q

how does oestrogen affect GnRH

A

high oestrogen (above 200) will increase GnRH pulsatility driving the release of LH

below 200 reduces frequency of GnRH pulses (FSH release)

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15
Q

why is modulation of LH pulse frequency needed

A

for pubertal maturation and reproductive function

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16
Q

what happens to GnRH in the onset of pubertal maturation

A

steady acceleration i GnRH pulsatility (peak at night- boys causes peak in testosterone in morning, erections)

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17
Q

what are the signs of delayed puberty

A

no period by age of 15

boys no sign of testicular development by age 14

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18
Q

how is GnRH pulsatility regulated

A

GnRH neurones activated by kisspeptin as dont have receptors for oestrogen and progesterone (the hormonal regulators)

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19
Q

what is the variable part of the menstrual cycle

A

follicular (proliferative phase) typically 14 days +/- 7 days

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20
Q

what is the follicular phase characterised by

A

follicular growth

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21
Q

what is the more constant phase of the menstrual cycle

A

luteal phase (secretory phase)

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22
Q

what causes the LH surge

A

when high oestrogen causes positive feedback

23
Q

why does FSH cause an increase in oestrogen

A

as follicles produce oestrogen

24
Q

what does LH surge causes

A

ovulation, regulates the formation of the corpus luteum, progesterone production and secretion (from follicle)

25
Q

how does increasing progesterone affect LH

A

decreases LH secretion by influencing GnRH pulsatility

26
Q

what does increasing progesterone do to LH secretion

A

decreases it by influencing GnRH pulsatility

27
Q

what hormone dominates the luteal phase

A

progesterone

28
Q

what makes up a follicle

A

an oocyte surrounded by folicular cells (granulosa cells, theca cells)

29
Q

happens happens to the follicle during its growth

A

increase in the number of follicular cells and accumulation of follicular fluid (increases in diameter and size)

30
Q

what effect does oestrogen have on the endometrium

A

thickens

31
Q

what effect does progesterone have on the endometrium

A

causes it to become a secretory tissue

32
Q

what hormone stimulates follicular growth

A

FSH (granulosa cells)

LH (theca cells)

33
Q

what happens in follicular growth if there is a lack of FSH

A

build up of androgens

34
Q

how many follicles in each ovary

A

7 million
2 million at birth
0.5 million at puberty

35
Q

how can FSH determine if a follicle is lost or not

A

when reaches certain size follicle becomes gonadotrophin dependent (2-5mm), if this doesnt coincide with rise in FSH during early follicular phase then follicle is lost

36
Q

how many follicles are selected for ovulation

A

1 (5/6 grow during each menstruation)

37
Q

what can predict the timing of ovulation

A

the LH surge (precedes ovulation by 34-36 hours)

38
Q

what happens to progesterone in LH surge

A

increases- essential for ovulation as stimulates enzymes that break down follicular wall releasing enzymes

39
Q

what hormone causes the formation of the corpus luteum

A

LH

40
Q

how do cells form the corpus luteum

A

granulosa and theca cells transform into luteal cells

41
Q

how does LH cause the formation of the luteal corpus

A 
stimulates angiogenesis (ensures delivery of cholesterol which is the synthesis for progesterone synthesis) 
stimulates enzymes involved in conversion of cholesterol to progesterone
42
Q

what are the functions of oestrogens

A

increases the thickness of the vaginal wall
regulate the LH surge
reduce vaginal pH though increase in lactic acid production
decreased viscosity of cervical mucous to facilitate sperm penetration

43
Q

what is the role of progesterone

A 
maintains the thickness of the endometrium 
creates infertile thick mucous (prevents sperm and infection) 
relaxes myometrium (smooth muscle)
important in maintaining pregnancy
44
Q

what hormones control spermatogenesis

A

LH and FSH and testosterone

45
Q

how long does spermatogenesis take

A

70 days

46
Q

what makes up the testes

A

seminiferous tubules surrounded by interstitial tissue

47
Q

what is in the intratubular compartment of the testes

A

sertoli and germ cells

48
Q

where does spermatogenesis take place

A

in the seminiferous tubules in the testes

49
Q

what is in the seminiferous tubules

A

sertoli cells and maturing germ cells surrounded by peritubular myoid cells

50
Q

what cells are stimulated by FSH to start spermatogenesis

A

sertoli cells

51
Q

what receptors do leyid cells (in testes) have

A

LH receptors- when bound secrete testosterone

52
Q

what paracrine factors affect spermatogenesis

A

testosterone and inhibin

53
Q

what is the role of testosterone in spermatogenesis

A

maintains the blood testes barrier

causes the release of mature spermatozoa from sertoli cells by influencing peritubular myoid cells

Endocrinology (46 decks)

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